Discrete element numerical simulation of two-hole synchronous hydraulic fracturing

The evolution law of hydraulic fracture propagation and the fracture mode of two holes synchronous hydraulic fracturing under the influence of different factors were studied. Results showed that when the azimuth angle of two holes is 0° (θ = 0°), the stress at the center of the rock sample can be divided into three stages: the stress rising stage before crack initiation, the stress slowing stage before the cracks intersection, and the stress sharp rising stage before crack penetration. Besides, at the moment of the intersection of cracks between holes, the central stress of the rock sample will rise sharply, and the closer the two holes are, the more serious the failure of the rock mass is. When the azimuth angle of two holes is greater than 0° (θ > 0°), due to the influence of tress shadow effect, the main crack migrated to the high-stress area and inclined cracks were produced between the two holes. When the horizontal distance between the holes is less than 5 times of the hole diameter, and the azimuth angle θ ≤ 30°, the fracture mode of the rock mass is changed from single fracture splitting to multi crack cutting. The research results can provide some theoretical guidance for synchronous fracturing of vertical wells. Article highlights The discrete element numerical (DEM) model of two-hole synchronous hydraulic fracturing is established to realize the liquid-solid coupling calculation. The azimuthal angle and spacing affect the fractures propagation and fracture pressure The increase of water injection rate or decrease of principa stress difference is more conducive to forming fracture network. The stress shadow effect between two holes is easy to induce hydraulic fracture migration.